Shudder judder at speed when braking

I'm back on a bike after a a long period off with a busted elbow, got myself a spanking new TCR Composite with ultegra brakes/groupset (all the gear and truly no idea)

I tackled my first proper climb on Monday for a year and I think reasonably cautiously wanted to use my brakes on the way down... however at speed upon approach to the first corner, put on the front brake and experienced a judder which came up the fork like I've not known before, while it was happening (through the terror) I thought it could be a loose headset, front brake and it even crossed my mind that I may not have tightened the front QR skewer !

While my mate fearlessly swept around the corners and crept up to 47/48mph I 'juddered' down in sheer terror at 44mph for the (0.5mile @ 12% avg) decent.

I've read quite a lot of this shudder and most people say it's the brakes, my question is what should i do about it? it's a new bike is it a warranty issue? setup issue? could it be that my headseat which don't appear to be loose..

Degrease the brake block and the rims, just sounds like it's grabbing at something, then you get a death grip on the bars and it gets worse.

Mate just got the top of the range Defy and both wheels more or less fell apart in the first 100 miles, local wheel shop spent a bit of time on them getting the tension up and level and they've been fine since.

Tacx make a brilliant jig for getting your brakes toed in correctly. Pads will wear to be parallel to the rims after a while so it needs re-doing occasionally. While you're there clean your rims and roughen up your pads as they could be glazed.

Could also be a problem with your rim or the wheel being out of true - give it a spin and see whether there's a wobble.

I'd have thought that an out-of-true wheel, at that speed, would tend to cause a wobble regardless of whether the brakes were being applied or not? Likewise for a loose headset.

It sounds definitely like a brake set-up issue. Pauldmorgan's suggestion of the Tacx brake jig is a good idea, else take it back to the shop you got it from and ask them to check the brake pad alignment.

Definitely sounds like the headset to me. One of the scariest moments I've had a on a bike was descending when my headset hadn't been tightened properly.

You probably already know this but the easiest way to check the headset is to hold the front brake on and watch the fork crown as you try to move the bike back and forth. See if there's any movement at all.

I had the problem of a very sharp knocking it turned out to be a faulty headset after i'd replace that I was getting a slight Judder still
After cleaning the rims/breaking surface with alcohol wipes it eliminated the problem